as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Example Sentences
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Recent Examples of insidious
But most of its failures are subtler, more insidious.
—
Katy Waldman,
New Yorker,
10 June 2026
What makes this deal particularly insidious is the trade-off at its core.
—
Joe Wilkins,
Futurism,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Katy Waldman,
New Yorker,
10 June 2026
What makes this deal particularly insidious is the trade-off at its core.
—
Joe Wilkins,
Futurism,
10 June 2026
But there is an insidious quality.
—
Rory McDonald,
Fortune,
6 June 2026
Best known for comedy series like Community (2009-15) and GLOW (2017-19), Alison Brie is taking on the role of Evil-Lyn, an insidious enchantress who serves as Skeletor’s main accomplice.
—
Keith Langston,
PEOPLE,
6 June 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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After death, the garden becomes more treacherous.
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For 250 years, between 1565 and 1815, the famous galleon fleet left the port of Manila for the port of Acapulco and back, traveling for months over the treacherous ocean while carrying a lucrative flow of foods, silver, fabrics and culinary traditions.
Adjective
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Available in a style with the same stripes that Paltrow favors, the top offers a subtle pattern that’ll make your outfit pop.
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The square neckline adds a flattering, feminine touch, while the subtle volume in the sleeves gives it a slightly dressier feel than your average tee.
Adjective
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The charge alleges a person knowingly defrauded another by using false or misleading information to obtain money, property, credit or a loan.
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Opponents of Amendment 5 have flatly called the advertisement misleading or false.
Adjective
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Shadow fleet vessels disguise their identity and purpose through a broad range of deceptive activities, including spoofing their locations and destinations.
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The complaint alleged deceptive advertising and other misconduct.
Adjective
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This is perhaps the most perfidious practice of this sort of politics.
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The government took a genuine invitation to collaborate as a perfidious power grab.
Adjective
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Released Parties are also not responsible for any incorrect or inaccurate information, whether caused by site users, tampering, hacking, or by any equipment or programming associated with or utilized in the Giveaway.
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At the same time, The New York Times reported that Google’s AI Overviews produced incorrect answers roughly one in 10 times.
Adjective
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Something told me that there was something wrong.
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The interest rate hypothesis points the wrong direction — the most rate-sensitive occupations, like construction, have the lowest AI exposure.
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 2 Jul. 2026.
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